Herpes Simplex Keratitisalso known as Ocular Herpes

Herpes simplex keratitis (HSK) is a corneal infection caused most often by herpes simplex virus type 1 (HSV-1). Episodes can range from mild surface irritation to deeper inflammation that may scar and blur vision. After a first infection, the virus can lie quiet in nearby nerves and reactivate later, so flares can come and go. With early diagnosis and the right treatment, most people recover well and protect their sight. [1] [2]

HSK usually affects one eye. Common symptoms include eye pain, redness, tearing, light sensitivity, and blurred vision. Doctors often see a classic branching (dendritic) sore on the corneal surface that takes up fluorescein dye. If deeper layers are inflamed (stromal or endothelial disease), vision can be more blurred and recovery slower. Sudden severe pain, halos, or fast vision changes deserve same-day eye care. [3] [4]

Most cases are due to HSV-1 (the cold-sore virus). After a prior exposure, the virus can reactivate and travel along nerves to the cornea. Triggers and risks include fever or illness, stress, intense sunlight/UV, eye injury or surgery, and use of corticosteroid eye drops without antiviral cover. Immunosuppression also raises risk. Past HSK is the strongest predictor of future flares. [5] [6]

Clinicians diagnose HSK at the slit lamp (microscope). Fluorescein dye helps reveal a dendritic ulcer with terminal bulbs in epithelial disease. They also check corneal sensation (often reduced) and look for signs of deeper inflammation like stromal haze or keratic precipitates. When the picture is unclear, a swab for PCR or culture may be used. Early, accurate diagnosis guides safe therapy and prevents scarring. [7] [8]

Epithelial HSK: Treat with antivirals (topical ganciclovir gel or trifluridine; often oral acyclovir or valacyclovir). Avoid steroid eye drops unless an eye specialist adds them with antiviral cover.

Stromal/endothelial HSK: Inflammation is largely immune-mediated; typical care combines a topical steroid plus concurrent antiviral (topical or oral). For people with frequent recurrences, daily oral acyclovir can cut flares and protect vision, as shown in NIH-supported HEDS results. [9] [10]

Act quickly if symptoms start—pause contact lenses and call your eye doctor. Protect your eyes from strong sun (UV), manage stress and sleep, and avoid eye rubbing. Use medicines exactly as prescribed and never start leftover steroid drops on your own. Keep lenses and cases clean and replace them after an episode. Ask your clinician if you’re a candidate for daily antiviral prevention, especially after stromal disease. [11] [12]

NEI-highlighted studies point to future options beyond standard antivirals. Wayne State researchers reported a potential mechanism that may shield some eyes from developing herpes stromal keratitis, suggesting new anti-inflammatory targets. Other work from University of Illinois Chicago implicates heparanase in HSV-1 reinfection, a host pathway that could be druggable to reduce recurrences. These advances are early but promising. [13] [14]

If you have new redness, light sensitivity, or blurry vision—especially with a history of HSK—seek a same-day exam with an ophthalmologist, ideally a Cornea specialist. Ask for an urgent slot; many clinics reserve time for suspected corneal infections. Keep all follow-ups so your clinician can confirm healing and adjust drops. You can also connect on Kerbside for a medical education consult with the right specialist (no patient-physician relationship will be established). [15] [16]